Recycled Carbon Fiber Research Articles

Investigation on Stress Relaxation of Discontinuous Recycled Carbon Fiber Composites

Investigation on Stress Relaxation of Discontinuous Recycled Carbon Fiber Composites

Investigation of the resin infusion process and mechanical performance of carbon fiber reinforced plastic composites from recycled carbon fiber

The disposal of Fiber Reinforced Composites (FRCs) waste is becoming a very critical aspect, from both a technical and an economic point of view, due to the continuous increase of the production of such a class of materials. Thus, the possibility to produce new composites by employing recycled materials is a crucial aspect both to guarantee the circularity of the manufacturing processes and the reduction of costs. In this work, the manufacturing process, together with the performance of a carbon fiber-reinforced plastic (CFRP) laminate obtained by employing into sandwich structures a novel commercial recycled non-woven carbon fabric with an epoxy resin, have been investigated. The fabrication process based on the Resin Infusion under Flexible Tooling (RIFT) has been selected and performed in different conditions. The mechanical behavior of the resulting laminates has been investigated by quasi-static tensile, and flexural characterization, to evaluate both the optimal conditions for the process, and the possible anisotropy of the product. Moreover, thermogravimetric analysis (TGA) was applied to complete the post-processing characterization of the resulting laminate by determining the actual carbon fibers (CFs) content, thus, to validate the reproducibility of the manufacturing process. The laminates obtained by the RIFT method exhibited good mechanical properties and isotropy if cross-ply stratification is adopted. The use of recycled CFs allows high sustainability and reduced cost for the composites, making the RIFT method investigated a scalable process and the so-manufactured products a valid candidate for numerous applications.

Facile preparation, closed-loop recycling of multifunctional carbon fiber reinforced polymer composites

Recyclable carbon fiber reinforced polymer (CFRP) composites have attracted considerable attention in recent years due to the combined merits of excellent mechanical and thermal properties, recyclability and reprocessability. This paper reports on the successful preparation of closed-loop recyclable CFRP by in-situ polymerization and dynamic cross-linking (ISPDC) technology. The SEM, XPS and monofilament tensile curves were measured to investigate the morphology, chemical details, and mechanical properties of the recycled carbon fiber (CF); the chemical structure of the degraded resin was further characterized and analyzed according to the NMR and FTIR spectra. The obtained results show that under mild acidic conditions, the CFRP was degraded to high-quality recycled CF and linear polymer with methacrylic acid units, which can be used to prepare regenerated CFRP. In addition, due to the dynamic feature of the hemiacetal ester structure in the CFRP matrix, the CFRP also exhibited multiple functions, such as rapid welding, reprocessing, shape shifting, and self-healing, as well as the extremely long shelf life of composite prepregs. Our analysis of the recycling and dynamic exchange processes indicates that the strategy of embedding a releasable linker is dominant for the preparation of closed-loop recyclable and multifunctional CFRP.

Biochar and recycled carbon fibres as additions for low-resistive cement-based composites exposed to accelerated degradation

Biochar (BCH) and recycled carbon fibres (RCF) were used as carbonaceous additions in low-resistive mortars/concretes. Their effects on mechanical, electrical, and durability properties were investigated. Tests were performed both during curing and accelerated degradation. The combined use of RCF and BCH decreased the electrical impedance of cement-based matrices, enabling the use of low-cost monitoring instrumentation, and improved their mechanical performance. Recycled carbon fibres and biochar additions increased carbonation and capillary water absorption but acting as a barrier they made water and chlorides penetrate less deeply.

Recycled Carbon Fibers with Improved Physical Properties Recovered from CFRP by Nitric Acid

To effectively reuse a large amount of Carbon Fiber Reinforced Plastics (CFRP) waste, the carbon fibers should be able to be recovered without degrading their quality. In this report, we developed a new approach to recover carbon fibers from CFRPs with improved physical properties compared to virgin carbon fibers with an environmentally friendly recycling method using nitric acid. Following the decomposition of the CFRP waste in nitric acid at 80 °C, both recycled carbon fibers and decomposed resin were recovered. The obtained recycled carbon fibers showed 1.4 times higher tensile strength and 2.2 times higher interfacial shear strength to resin compared to virgin carbon fibers. TEM-EDX analysis showed a decrease in the abundance of voids existing in the carbon fiber surface layer and new polar functional groups caused by nitric acid existing inside the voids, leading to increased tensile strength. Furthermore, XPS analysis showed that the interfacial shear strength improved due to the formation of new polar functional groups due to nitric acid. The possibility of applying recycled carbon fibers to CFRP products was shown by elucidating the mechanism that expressed its physical properties during the recycling process, leading to a novel approach to realizing closed-loop recycling.

Recyclable, Repairable, and Fire-Resistant High-Performance Carbon Fiber Biobased Epoxy

Due to the global environmental concerns caused by the ever-increasing environmental impact, landfill materials, and CO2 emission, there is a critical need in the elaboration of sustainable composite materials. Advanced material composites used in the production of high-performance products to solve some of the most difficult engineering challenges are having a key role in decarbonization by their light weight, higher performance, and increasing durability. In this work, sustainable carbon fiber reinforced composites (CFRCs) have been engineered with an environmentally friendly epoxy resin derived from natural and renewable compounds employing an industrial feasible manufacturing protocol. The thermosetting resin with a biobased organic carbon content (BOC) of ∼77% was synthesized by combining a renewable based monomer, the triglycidyl ether of phloroglucinol (TGPh), with hexahydro-4-methylphthalic anhydride (HMPA). The developed CFRCs show high performance with high glass transitions Tg > 350 °C, a high storage modulus ∼42 GPa, a high interlaminar shear strength ∼63 MPa, and a compressive strength ∼400 MPa. In addition, the outgassing tests show that both the resin and the CFRCs are compliant for space application. Moreover, the biobased CFRCs exhibit chemical recyclability, reprocessability, and excellent intrinsic flame resistance.

Recyclable, reprocessable, self-healing elastomer-like epoxy vitrimer with low dielectric permittivity and its closed-loop recyclable carbon fiber reinforced composite

Epoxy resin with reprocessable, strong mechanical property and mutil-functions (such as recyclable and dielectric properties) shows great prospects in many applications, but it is still a huge challenge. Herein, we combine siloxanes and dynamic transesterification reaction to fabricate a novel closed-loop recyclable elastomer-like epoxy vitrimer (ETOD-SA) with high stretchability (135%), low dielectric permittivity (2.75), reversible deformation (30 cycles) as well as rapid self-healing (10 min for a 36 μm scratch). The ETOD-SA is optimized to achieve excellent shape memory and reprocessing properties due to dynamic transesterification reactions catalyzed by internal tertiary amines in the structure of ETOD-SA vitrimer. Furthermore, carbon fiber reinforced ETOD-SA composite (ETOD-SA-CF) also exhibits excellent self-healing, shape memory, degradable properties and has prospective application in recyclable carbon fiber reinforced composite. Due to the rapid chemical degradation of ETOD-SA under mild conditions in the presence of ethanol or butylamine, carbon fibers (CFs) of ETOD-SA-CF can be effectively recycled in a closed loop. The performance of recycled carbon fibers are similar to those of original ones, with almost the same chemical structure and mechanical properties. These results provide an important strategy for the development of mutil-functions epoxy vitrimer materials and their practical applications in the closed-loop recycling of CFs from carbon fiber reinforced composites (CFRPs).

Investigation of recycling effects on the mechanical properties of short carbon and glass fiber reinforced polyetherimide composites

AbstractConsidering the increasing composite waste accumulation, this work explores the feasibility of replacing virginal carbon fibers (VCFs) and virginal glass fibers (VGFs) with recycled fibers for injection molded polyetherimide (PEI) composites. Extensive characterizations were conducted to reveal effects of sulfuric acid recycling process on mechanical properties of fibers and their composites. It was shown that strength retention rates of recycled carbon fibers (RCFs) and recycled glass fibers (RGFs) were 81.6% and 55.7%. The reinforcing factor of RCFs increased from 0.120 of VCFs to 0.147 due to the enhanced interfacial bonding while the reinforcing factor of RGFs decreased from 0.080 of VGFs to 0.065 owing to the glass fiber strength reduction. As a result, the composite tensile strength (152.8 MPa) of RCF/PEI was comparable to that (155.3 MPa) of VCF/ PEI and RGF/PEI tensile strength (102.5 MPa) was lower than that (112.3 MPa) of VGF/PEI. Moreover, the tensile modulus of RCF/PEI and RGF/PEI were also approximatively comparable to those of VCF/PEI and VGF/PEI since recycling process showed a slight effect on fiber modulus. Although there exists an impact of recycling on fiber mechanical properties, the introduction of recycled fibers (especially RCFs) by injection molding process can promisingly enhance PEI composites.

Theoretical modeling of tensile properties of thermoplastic composites developed from novel unidirectional recycled carbon fiber tape structure

This paper aims to conduct theoretical modeling of tensile properties of thermoplastic composites developed from novel unidirectional recycled carbon fiber tapes. Unidirectional recycled carbon fiber tape structure is an innovative, sustainable and cost-efficient prepreg structure designed to develop carbon fiber reinforced plastics with the highest resource efficiency. In order to do modeling, existing theoretical models of tensile properties of unidirectional composites were reviewed in the first part of this paper. Subsequently, reviewed theoretical models were further modified by considering the tensile properties of fibers, fiber length, fiber orientation, fiber volume content and short fiber content to predict the tensile properties of composites based on novel tape structure. The results of this study reveal that the proposed theoretical models are in good agreement with the experimental results.

Recycled Carbon Fibre Composites in Automotive Manufacturing

Article Recycled Carbon Fibre Composites in Automotive Manufacturing Jean-Baptiste R. G. Souppez 1, * , and Geethanjali S. Pavar 2 1 Department of Mechanical, Biomedical and Design Engineering, School of Engineering and Technology, College of Engineering and Physical Sciences, Aston University, Birmingham B4 7ET, UK. 2 Institute for Energy Systems, School of Engineering, University of Edinburgh, Edinburgh EH9 3JW, UK. * Correspondence: j.souppez@aston.ac.uk Received: 9 January 2023 Accepted: 22 February 2023 Published: 6 March 2023 Abstract: The contemporary need for lightweight and sustainable materials in automotive manufacturing has made recycled carbon fibre an attractive option. Yet, aspects such as the mechanical properties of short fibre composites need to be characterised to fully identify the capabilities and opportunities for recycled carbon fibre in the automotive industry. Consequently, this paper aims to ascertain the potential of recycled carbon fibre materials for automotive manufacturing by considering mechanical properties, design implications, and resulting costs and sustainability. Destructive testing is employed to characterise the mechanical properties of virgin carbon fibre (VCF), recycled carbon fibre (RCF) using pyrolysis, and blended recycled carbon fibre (BRCF) comprising 50% polypropylene fibre. Here we quantify (i) the reduction in mechanical properties, namely the tensile modulus and breaking strength, (ii) the resulting increase in required thickness and therefore mass for manufactured parts and (iii) the reduction in cost and embodied energy achieved for RCF and BRCF compared to VCF, based on both a stiffness- and a strength-driven design criterion. Furthermore, we present a decision-making methodology revealing BRCF as the most cost-effective solution, while RCF proves to be the most sustainable alternative. These results provide a novel quantitative assessment of recycled carbon fibre for automotive manufacturing and may contribute to future developments in sustainable composite manufacturing in the automotive industry.

The properties of fibre-reinforced calcium phosphate cement composites under prolonged increasing cyclic thermal loads

This work is focused on thermo-mechanical behaviour of fibre-reinforced calcium phosphate cement (CPC) under thermal load. Macro-polypropylene, amorphous metallic and recycled carbon fibres at a dosage of 1.5% by volume were individually incorporated into a molten premixed plain CPC to improve its fracture behaviour. The tested specimens with dimensions 40x40x160 mm3 were first autogenously cured at room temperature for 14 days before being exposed to a temperature of 50 °C-1000 °C in an oven. The thermal resistance of the cement composites was then investigated. The residual properties observed in non-destructive and destructive experiments showed that the strength of CPC composite material is affected by extreme heat. Nevertheless, this material holds great potential for refractory applications.

Crashworthiness of recycled carbon fiber composite sinusoidal structures at dynamic rates

Fiber reinforced polymer composites are finding applications in the automotive space for structurally critical applications including crash management. The use of recycled carbon fiber reinforcement can greatly reduce carbon emissions. In this study, recycled carbon fiber composites were manufactured into a self-supporting geometry using three matrices: polyphenylene sulfide (PPS), acrylonitrile butadiene styrene (ABS), and a structural epoxy, and subsequently crushed between flat platens at dynamic rates ranging from 4.6 to 9.1 m s−1 at temperatures in a range of −40 °C to 80 °C. Load-displacement data was used to evaluate their specific energy absorption, crush efficiency, and steady-state crush stress. The energy absorption of the ABS composites was strongly sensitive to temperature, while the PPS composites exhibited strong crush efficiency dependence with both rate and temperature. The epoxy composites exhibited stable crush behavior at dynamic crush rates but exhibited a dramatic reduction in crush efficiency relative to quasi-static tests. The results of this study indicate that recycled fiber composites can achieve very high energy absorption levels (50–80 kJ kg−1 at room temperature) that make them an excellent alternative to more expensive and less environmentally friendly continuous virgin fiber laminates.

Utilization of Mechanically Recycled Carbon Fibers in Vinyl Ester Composites.

As we enter the twenty-first century, the aviation sector is expected to thrive as flying becomes the primary mode of transportation between states or nations. With such a demand, there is a corresponding need to manufacture aircraft components. The study focused on recycling carbon fiber composites received from the STRATA company, which were cut-off/waste material generated during the manufacture of airplane components. The cut-offs were then reduced to powder form using a standard face milling machine in three sizes (90, 150, and 250 µm). After, the powder was utilized to fabricate vinyl ester composites with four weight percentages (10%, 20%, 30%, and 40%). The results demonstrate that the tensile strength of all composites had risen by 30.2%, 21.3%, and 17.6% for 90, 150, and 250 µm respective with the addition of 20 wt% of reinforcement. Furthermore, subsequently decreased with the additional reinforcement for all particle sizes. The compressive strength increased by 30% from 187.5 MPa to 244 MPa with 10 wt% of recycled carbon powder composite of 90μm particle size. However, samples prepared with 150 μm and 250 μm fiber size show approximately 17% and 1% increase in the compression strength with the addition of 10wt% of recycled carbon powder. A similar trend was observed for the flexural strength with an highest increase of 9% for 90 µm particle size with addition of 20 wt% reinforcement. Nonetheless, the SEM images revealed that the fiber-matrix bonding was weak, proved through the clean pullout fibers at the fracture surfaces.

Mechanical Behaviors of Microwave-Assisted Pyrolysis Recycled Carbon Fiber-Reinforced Concrete with Early-Strength Cement

This study aimed to investigate the mechanical performance of early-strength carbon fiber-reinforced concrete (ECFRC) by incorporating original carbon fiber (OCF), recycled carbon fiber (RCF), and sizing-removed carbon fiber (SCF). Compressive, flexural, and splitting tensile strength were tested under three fiber-to-cement weight ratios (5‱, 10‱, and 15‱). The RCF was produced from waste bicycle parts made of carbon fiber-reinforced polymer (CFRP) through microwave-assisted pyrolysis (MAP). The sizing-removed fiber was obtained through a heat-treatment method applied to the OCF. The results of scanning electron microscopy (SEM) analysis with energy dispersive X-ray spectrometry (EDS) indicated the successful removal of sizing and impurities from the surface of the RCF and SCF. The mechanical test results showed that ECFRC with a 10‱ fiber-to-cement weight ratio of carbon fiber had the greatest improvement in its mechanical strengths. Moreover, the ECFRC with 10‱ RCF exhibited higher compressive, flexural, and splitting tensile strength than that of benchmark specimen by 14.2%, 56.5%, and 22.5%, respectively. The ECFRC specimens with a 10‱ fiber-to-cement weight ratio were used to analyze their impact resistance under various impact energies in the impact test. At 50 joules of impact energy, the impact number of the ECFRC with SCF was over 23 times that of the benchmark specimen (early-strength concrete without fiber) and was also greater than that of ECFRC with OCF and RCF.

Investigating the Effects of Nitric Acid Treatments on the Properties of Recycled Carbon Fiber.

In this study, the chemical state change of recycled carbon fiber (rCF) surfaces and the mechanism of the oxygen functional groups according to nitric acid treatment at various times and temperatures were investigated to upcycle the carbon fiber recovered from used carbon composite. When treated with nitric acid at 25 °C, the carbon fiber surface demonstrated the same tensile properties as untreated carbon fiber (CF) for up to 5 h, and the oxygen functional group and polar surface energy of C-O (hydroxyl group) and C=O (carbonyl group) increased slightly compared to the untreated CF up to 5 h. On the other hand, at 100 °C, the tensile properties slightly decreased compared to untreated CF up to 5 h, and the amount of C-O and C=O decreased and the amount of O=C-O (lactone group) started to increase until 1 h. After 1 h, the amount of C-O and C=O decreased significantly, and the amount of O=C-O increased rapidly. At 5 h, the amount of oxygen functional groups increased by 92%, and the polar surface energy increased by 200% compared to desized CF. It was determined that the interfacial bonding force increased the most because the oxygen functional group, O=C-O, increased greatly at 100 °C and 5 h.

Micro-Scale Model of rCF/PA6 Spun Yarn Composite

Recycling carbon fibers (rCF) for reuse is one approach to improve the sustainability of CFRP. However, until now, recycled carbon fiber plastics (rCFRP) had limited composite properties due to the microgeometry of the fibers, which made it difficult to use in load-bearing components. The production of hybrid yarns from rCF and PA6 fibers allows the fibers to be aligned. The geometric properties of the yarn and the individual fibers influence the mechanical properties of the composite. An approach for the modeling and simulation of hybrid yarns consisting of recycled carbon fibers and thermoplastic fibers is presented. The yarn unit cell geometry is modeled in the form of a stochastic fiber network. The fiber trajectory is modeled in form of helical curves using the idealized yarn model of Hearle et al. The variability in the fiber geometry (e.g., length) is included in form of statistical distributions. An additional compaction step ensures a realistic composite geometry. The created model is validated geometrically and by comparison with tensile tests of manufactured composites. With the validated model, multiple parameter studies investigating the influence of fiber and yarn geometry are carried out.

Additive manufacturing-inspired approach to re-manufacture fiber reinforced plastic with programmable orientation of recycled carbon fiber

The carbon fiber recycled from end-of-life Carbon Fiber Reinforced Plastic (CFRP) offers a low-cost and environmentally friendly option to produce CFRP parts. However, the reclaimed carbon fibers (rCFs) are usually in a discontinuous and disordered form, which limits the performance of fiber-filled composite. An additive manufacturing-inspired approach is proposed to re-manufacture CFRP, in which the rCFs were dispersed and orderly deposited to form a slice of pre-defined rCF sheet with programmable fiber orientation, then the rCF sheets were stuck layer by layer to fabricate aligned rCF reinforced plastic (rCFRP). Experiments show that preferential alignment degree, flexible strength and electric conductivity of designedly aligned rCFRP were 0.96, 393.53 MPa and 7.23 × 10−1 S/cm, respectively, which are significantly higher than the unoriented rCFRP (0.28, 217.59 MPa and 1.07 × 10−2 S/cm). This approach paves the way for additively fabricating rCFRP parts with customized performance by arranging rCFs orientation.

Development of a method for recycling factory waste carbon fiber prepregs and increasing the added value of the collected material

AbstractCarbon fiber reinforced plastics (CFRPs) are widely used in the aerospace, automotive, and construction industries. CFRP prepregs (intermediate products) are generally used in CFRP production, with a large number of prepreg cut‐offs being discarded during cutting processes. There is strong demand for a method for recycling carbon fiber prepreg cut‐offs. This paper proposes a method for recycling such material, which is characterized by low cost and high added value, in order to foster the development of a recycling‐oriented society. We prepare carbon tapes (CTs) by cutting discarded cut‐offs according to their size so as to maximize fiber length. Using a simple water CT dispersion method, we fabricate uniform CT sheets and mold a recycled CT‐reinforced composite (R‐CT‐RC). Sample prototyping and mechanical characteristic testing indicate that this R‐CT‐RC is characterized by low recycling cost and desirable mechanical properties. Recycled CT‐reinforced composite with thermoplastic (R‐CT‐RC/TP), which is prepared by adding thermoplastic resin between CTs, can be re‐molded and therefore readily re‐recycled.

Ultrasonic pulse velocity and physical properties of hybrid composites: A statistical approach

This work describes the correlations between the ultrasonic pulse velocity (UPV) and physical properties of fibrous-particulate hybrid composites made of glass/carbon fabrics and three different micro-inclusions such as silica particles, recycled carbon fibre powder and Portland cement. A full factorial design (214151) is established to identify the effects of volume fraction, stacking sequence and particle type on the physical properties obtained by Archimedes’ principle. An electroacoustic transducer (50 ​kHz) is used to determine the ultrasonic pulse velocity data. Statistical models reveal correlations between UPV and the physical properties of hybrid composites. The combination of UPV and statistical techniques can identify all constitutive phases, being useful to characterise and estimate physical properties in a hybrid system composed of fibres and microparticles.

Performance of silica fume slurry treated recycled aggregate concrete reinforced with carbon fibers

The utilization of recycled concrete aggregate (RCA) is a sustainable way to produce concrete. However, using recycled aggregate in concrete results in inferior mechanical performance and durability, mainly due to the weak interfacial transition zone (ITZ) and attached mortar. The research aims to overcome the inferior properties of recycled aggregate concrete (RAC) by treating recycled aggregate with silica fume (SF) slurry and carbon fibers (CF) as reinforcement. A total of thirteen mixes were prepared and tested for workability, water absorption, mechanical strength, elastic modulus and performance against acid attack. To optimize the performance of recycled concrete, carbon fiber and silica fume were employed at 0.5% and 10%, respectively, with 25%, 50%, and 100% substitution levels of recycled aggregates. The aggregate was pre-soaked in SF slurry for 24 h before mixing in concrete to ensure its absorption or adherence to aggregate. Compressive, split tensile, and flexure strengths of recycled aggregate concrete were evaluated at 7, 28, and 56 days. Elastic modulus was examined under axial compression at 28 days of curing age. Experimental results showed that SF improves the microstructure of cement paste and the bonding between binder matrix and carbon fibers. Compressive, split tensile and flexural strength results of 45.2 MPa, 5.4 MPa and 7.8 MPa, respectively were observed by combined utilization of carbon fiber and silica fume at 28-day curing age in 100% recycled concrete i.e., for recycled concrete mix CFSF-RC100, which is 20%, 34%, and 46% more than their corresponding control mix i.e., RC100. Elastic modulus for RC mixes were found to vary between 22 GPa for RC100 mix and 35.6 GPa for CFSF-RC25 mix respectively. Silica fume also contributed to the water absorption reduction of up to 14% in recycled concrete. Carbon fiber-reinforced recycled concrete was more acid attack resistant having only 6.3% mass loss after acid attack and hence 40% reduced mass loss was observed compared to that of recycled aggregate concrete. Hence, strong, durable, and environment friendly concrete was produced.